Integrated circuit chips, such as micro-processor chips, and other electronic components generate heat during operation. These components are generally mounted on printed circuit boards (PCBs). To help ensure proper operation, these components generally are kept at an operating temperature below around 160° F. This means that cooling of some sort must be provided for proper operation of electronic components.
Cold plates are widely used for cooling PCBs where the coolant must be kept separated from the electronic components. A cold plate generally consists of an enhanced heat transfer surface encapsulated in a high aspect ratio rectangular duct. The enhanced heat transfer surfaces are typically some sort of fin arrangement or an open-celled, porous metal foam. Coolant flows through the cold plate from one end to the other end, completely wetting the enhanced heat transfer surface inside. This system cools PCBs mounted to the sides of the cold plate. Finned core stocks and metal foams are used in cold plates because they increase the thermal effectiveness by increasing the surface area available for transferring heat to the coolant. However, surface area densities for finned core stock and metal foams are generally limited to approximately 1000 ft2/ft3. This is chiefly because surface area densities significantly larger than this value result in unacceptably high pressure drop as the coolant flow through the cold plate. High pressure drop translates into a system penalty in the form of higher power required for pushing the coolant through the cold plate. Furthermore, manufacturing fin and metal foam arrangements with higher surface area densities becomes increasingly costly and complex. These limitations on surface area density ultimately limit the heat that can be absorbed for given coolant flowrate. Such a limitation will be exacerbated by introduction in the future of high power electronics because conventional air cooled cold plates will not be able to address cooling of future high power electronics. This is because these chips are projected to generate significantly more heat than contemporary chips while still having an operating temperature limit of around 160° F.
One of several possible applications for cold plates includes cooling PCBs found in avionics units on aircraft. Avionics cooling on aircraft is commonly provided by blowing cooled, conditioned air through cold plate heat sinks. However, generation of this cooling air by an aircraft environmental control system (ECS) constitutes a system performance penalty for the aircraft. This is because the ECS generates cooling air by extracting air from the aircraft's engine and cooling it with ram air ducted into the vehicle from outside. Extracting air from the engine reduces the air available for generating thrust while capturing ram air increases aircraft drag. These effects ultimately reduce range and/or payload for an aircraft.
Therefore, it would be desirable to reduce the amount of air required to cool avionics, thereby reducing the system performance penalty for an air vehicle by increasing vehicle thrust and/or lowering fuel consumption. It would also be desirable to address cooling of future high power electronics that are projected to generate significantly more heat than contemporary chips while still having an operating temperature limit of around 160° F. It would also be desirable to maximize thermal performance of a cold plate while mitigating change in pressure drop across the cold plate.
The foregoing examples of related art and limitations associated therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.